In order to brake automobiles, disc brakes are used widely.
The braking of automobiles by the disc brake is executed by pressing a pair of pads, which are disposed on the both sides in the axial direction of the disc rotor that rotates along with a wheel, against the both sides of the disc rotor by moving forward the piston inserted in a cylinder by oil pressure.
In such disc brake, cylinders provided to an inner caliper section and an outer caliper section, respectively, are connected via an oil channel provided inside a caliper body. Regarding such oil channel inside the caliper body, known is a structure where the oil channel is provided by molding by using a core (e.g., see Patent Document 1).
A piston-opposed type disc brake disclosed in Patent Document 1, as shown in FIGS. 18 and 19, an inner caliper section 102 and an outer caliper section 103 arranged in an opposing manner in a caliper body 101 are linked via a bridge section 104 that crosses over a disc rotor D. Further, the inner caliper section 102, the outer caliper section 103, and the bridge section 104 are formed integrally through casting by using aluminum or an aluminum alloy as a material thereof.
Two each of cylinders 105 and 105 are formed in the inner caliper section 102 and the outer caliper section 103, respectively, and pistons 106 and 106 are inserted to each of the cylinders 105 and 105, respectively, in a liquid-dense manner.
A window hole 108 is provided to the caliper body 101, and brake pads 107 to be slid against the disc rotor D by being pressed by the pistons 106, 106 are provided in the window hole 108 in a freely slidable manner in the direction along the disc axis.
Further, an inner-side cylinder connecting oil channel 110A and an outer-side cylinder connecting oil channel 110B extended towards the outer side of the radius direction of the disc rotor D for connecting between the inner bottom parts of each of the cylinders 105 and 105 are provided to the inner caliper section 102 and the outer caliper section 103, respectively.
Further, those cylinder connecting oil channels 110A and 110B are formed by using a decay core when casting the caliper body 101.
Further, a hydraulic linking channel 113 in the disc axial direction is provided to the bridge section 104 of the caliper body 101. A bleeder hole 114 that is coaxial with the hydraulic linking channel 113 is formed at the end part of the hydraulic linking channel 113 on the inner caliper 102 side, and an air bleeder 115 is screwed into the bleeder hole 114. Thus, the bleeder hole 114 is blocked.
The piston-opposed type disc brake is in the structure described above, so that each of the brake pads 107, 107 is pressed against the both side faces of the disc rotor D when the pistons 106, 106 are pressurized to the disc rotor D side via an oil pressure at the time of operation.
As a result, the pressurizing force of the brake pads 107, 107 works as the braking force for the vehicle axle, thereby decreasing the rotating speed of the vehicle axle or stopping it. That is, the brake comes in effect.
Patent Document 1: Japanese Unexamined Patent Publication 2010-101342
However, there are following issues with the existing technique described above.
That is, the cylinder connecting oil channels 110A, 110B formed to each of the inner caliper section 102 and the outer caliper section 103 are formed with a core placed inside the mold cavity at the time of manufacturing the caliper body 101, while the hydraulic linking channel 113 connecting between those cylinder connection oil channels 110A and 110B is opened by performing drill processing from the outer surface part of the inner caliper section 102, for example, after casting the caliper body 101.
However, the processing of the hydraulic linking channel 113 by drilling needs to open the hole of small diameter, and the hole opening processing is executed from the inner caliper section 102 through the outer caliper section 103 so that the processing length becomes long. As a result, the drill may be warped depending on the moving speed of the drill. Therefore, the processing is difficult and the processing precision may become poor, so that the yield is deteriorated as well.
Further, the processing of the hydraulic linking channel 113 by the drill is required to securely connect the end parts of each of the two cylinder connecting oil channels 110A and 110B which are located at positions that cannot be visually recognized from the outer surface part of the inner caliper section 102, so that the direction of the drill and the start position for opening the hole need to be determined surely. Therefore, it takes a long time to start up the hole opening processing.
Further, the processing of the hydraulic linking channel 113 needs to open the hole of small diameter and the processing length is long, so that it is required to advances the drill carefully. Thus, the processing time becomes long, thereby deteriorating the productivity. As a result, the cost performance becomes poor.
Further, even when the hydraulic linking channel 113 and the cylinder connecting oil channels 110A, 110B are connected in the above-described work, it is not possible to judge that the hydraulic linking channel 113 and the cylinder connecting oil channels 110A, 110B are connected in a 100% state. Supposing that a part of the channel 113 and a part of the channels 110A, 110B are connected, it is possible to check that those are linked by blowing air, for example. However, it is not possible to judge whether or not those are linked in a 100% state. If so, it is necessary to check whether or not the oil pressure is uniformly applied to the cylinders 105 of the inner caliper section 102 and the outer caliper section 103 through operating the pistons 106 by actually applying the oil pressure to the cylinders 105 to which the pistons 106 are mounted.
Further, in a case where the oil pressure is not applied uniformly to the cylinders 105 of each of the caliper sections 102 and 103, braking becomes unstable and uneven wear and the like of the brake pads 107 occur, thereby producing an inferior piece. Only after executing the work theretofore, the judgment regarding whether or not the caliper body 101 can be used as a product can be made finally. Therefore, it takes a lot of effort and time, so that the cost performance in regards to those is poor as well.
The present invention is designed to overcome the issues described above. More specifically, it is an object of the present invention to provide a caliper for disc brakes, which is capable of securely placing a hydraulic linking channel inside a bridge section which mutually links an inner caliper section and an outer caliper section without depending on machining.